>Grandfather paradox says the riders on the ship won’t experience most of the time of the ride
No. The Grandfather Paradox[0] says nothing of the kind:
The consistency paradox, commonly known as the grandfather paradox, occurs
when the past is changed in any way.[5] The paradox of changing the past
stems from modal logic: if it is necessarily true that the past happened in a
certain way, then it is false and impossible for the past to have occurred in
any other way, so any change to the past would be a paradox.[13] Consistency
paradoxes occur whenever any change to the past is possible.[6]
A common example given is a time traveler killing their grandfather before
their parents' conception, thus preventing the conception of themselves. If
the traveler were not born, they could not kill their grandfather; therefore,
the grandfather proceeds to beget the traveler's ancestor who begets the
traveler. This scenario is self-contradictory.[5] One proposed resolution for
this paradox is that a time traveller can do anything that did happen, but
cannot do anything that did not happen.[5] Another proposed resolution is
simply that time travel is impossible.[14]
[0] https://en.wikipedia.org/wiki/Temporal_paradox